1. Field of the Invention
The present invention concerns a method relating to powder metallurgical manufacturing of a body having a through hole, for example a hollowed tool blank or a thick-walled tube.
2. Discussion of Related Art
Hollowed tool blanks of high speed steels, hot or cold work steels, or advanced construction steels are used to a considerable extent for the production of various finished products. Examples of such products are cutting tools having a shaft, e.g. cutters, tool dies, linings in extrusion presses, gears and other machine elements. Among other technical fields may be mentioned the arms industry, where hollowed blanks can be used for the manufacturing of gun barrels.
The manufacturing of blanks by boring an urnhollowed working-piece is a costly task, particularly when it is the question of materials which are difficult to work by cutting operations, such as high speed steels and other tool steels, advanced construction materials, etc, whether the working-piece has been made powder metallurgically or by conventional production. Traditional powder metallurgical manufacturing by making a green body, which is subjected to subsequent sintering and working offers good opportunities of manufacturing hollowed blanks, while the manufacturing of hollowed blanks by hot isostatic compaction of metal powder implies substantially greater practical problems. It is true that it is possible to enclose the powder in a tube-shaped capsule, which is subjected to hot isostatic compaction, but the manufacturing and welding of such capsules is comparatively complicated and makes the manufacturing considerably more expensive.
It is also possible to provide a core in the capsule which is filled with metal powder and which is subjected to a subsequent hot isostatic compaction, whereafter the core can be removed after completed consolidation of the metal powder by hot isostatic compaction. The difficulty lies in the removal of the core, which integrates itself with the consolidated body which is formed of the metal powder at the hot isostatic compaction.